Variable-pitch propeller



Oct. 7, 1941. c: KELLER 2,258,094

. VARIABLE-1.?ITCH PROPELLER Filed Nov. 7, 1939 v 4 Sheets-Sheet 1attorin egs I Oct. 7, 1941. c, KELLER I 2,258,094

VARIABLE-PITCH PROPELLER Filed Nov. '7, 1959 4 Sheets-Sheet 2 ZSnnentorwuzmz e? (Ittomegs Oct. 7, 1941.- c. KELLER VARIABLE-PITCH PROFELLER 4'Sheets-Sheet '0' Filed Nov. 7, 1959 Oct. 7, 1941. c. KELLE RVARIABLE-PITCH PROPELLER 4 Sheets- Sheet 4 Filed Nov. '7, 1939 rotarymotion of the of the clutch disc Patented Oct. 7, 1941 UNITED STATE sPATENT oFr ca VARIABLE-PITCH PROPELLEB Curt Keller, Zurich,

Escher Wyn Masc selhchaft, of Switaerland Switzerland, allignor tohinenf abrieken Aktienge- Znrich, Switaerland, a corporationApplieaItionNovember 1, 1939, Serial No. aossos The propeller blades areindividually swiveled in a hub casing which is fixed on a tubular shaft.Also fixed on this shaft is a piston which works in a double actingcylinder'splined within the hub casing so that the cylinder cannotrotate relatively to the casing. This cylinder laconin such a w y thatas the'cylinder moves in the Switzerland November a cam. (91. m-issi' Inanother form of the spring action" and the retention of the clutchnected by 112% with the various propeller blades direction of he axis ofthe shaft, it rotates the -blades about their longitudinal axes and thusmodifies the pitch of the propeller. The piston fixed on the shaftencloses a dental clutch mechanism which locks the cylinder againstaxial motion except when the control device operates to establishhydraulic pressure tween the two ends of the cylinder to effect themotion of the cylinder and the consequent adjustment ofthe pitch of theblades.

This locking mechanism, which is an important feature of t theinvention, swiveled on the periphery of the piston and threaded toengage quick pitch thread grooves formed on the interior of the cylinderwall. It follows that axial motion of the cylinder entails ton. The ringhas on its internal surface an annular dental portion serving as onecomponent of a dental clutch, the other component being a clutch discwhich isaxially shiftable within the piston but which is 'heldagainstrotation relatively to the piston. Springs are used-todifferentials beincludes a ring ring relatively to the pisline an ofFig.

bias the disc to its mid position in which it engages the ring. I

To move the clutch disc in axial directions use is made ofa plurality ofsymmetrically arranged double acting pistons which also perform a valvefunction such as before pressure fiuid may fiow to either and from theother working space of the cylinder. Thus,- when hydraulic fluid isdelivered to oneand ventedfrom the other of the two ports which leadto'opposite sides of said valved pistons, the first effect is to displacethe .valved pistons which are always exposed to the pressure fluid inthese ports, withthe resultthat to insure the disengagement fluid ispermitted to of a link I" (see also the dental clutch fiow past thevalved pistons to one chamber and to bevented from the other chamber onopposite sides of the main piston to cause the cylinder to move axially.n

In one form of the invention the dental clutch disc is urged to itscenter or engaging position by sets of opposed springs which areassociated with means distinct from the valved pistons, clutch discbeing prevented in its engaging position from rotating relatively to themain piston. invention the centering ring against rotation areeach/performed by means directly associated with the valved pistons.Both arrangements have the advantage that the structure is perfectlysymmetrical and therefore perfectly balanced. Functionally they areessentially the same.

In the drawings:

Fig. l is an axial longitudinal section on the 2 through the firstconstructional form of a variable-pitch propeller to which the presentinvention is applied, only part of one of the blades being shown for thesake of cleamess; i

Fig. 2 is a section on the line 11-11 of Fig. 1,

Fig: 3 is an end view of a ,detail'seen in the direction of the arrowsIIIof Fig. 2.. Figs. 4 and 5, respectively, show on an enlarged scalethe motor mechanism similarly illustrated in Figs. 1 and 2, Fig. 5 beinga section on the line V-V of Fig. 4.

Fig. 6 is an axial longitudinal section through a portion of the secondconstructional form of the controlling device, and

Fig. 7 is a section on the line VII-'VII of Fig. 6, the upper coverofsthe main piston being removed.

Referring to denotes the'hub casing of an aeroplane propeller with threeadjustable-blades I02. Each of these blades I02 is fixed in a socketIII! which carries a pin I which is connected by means Fig. 3) with apin I" mounted on a cylinder l. formed with a pair or lugs-whichcoactwith a longitudinal rib Hi1 (see Fig. 2-) within the hub the cylinderispreventedfrom rotating relatively to the hub casing but may moveaxially relatively thereto. The cylinder 1 is mounted to slidelongitudinallyon the propeller shaft consisting of two concentric tubes2 i constituting a rigid unit. Any longitudipsi movement of the cylinderI is converted by is disengaged, whereupon the drawings, m (Figs. 1 tos) This cylinder I is v .the ports 4 oithe tubes 2 2 the links m me; arotary movement of the blades I32 so that the latter are adjusted in thedesired direction. The central opening provided by the inner tube 2enables shooting to be done through the hub of the propeller.

3 and 4 are twogroups of longitudinal ports formed by the walls of thetwo concentric tubes sure, preferably oil. The control valve H isactuated by a centrifugal governor H3 which is driven, together with thepump I I2, by the propeller shaft-2 2 I and 8 denote two parts of a mainpiston, which are rigidly mounted. on the tube 2 and held together bytwo cover discs I, 8. Hence the piston formed of the parts 5 to 9inclusive-is fixed relatively to the hub casing IOI. In the parts 5 and9 of the piston are two groups of bores 9, III which are arrangedaroundthe axis of the tubes 2 2 and run'parallel with this axis. Theaxes of all these bores 9, I9 lie on a cylindrical surface II (Fig. 5)which is coaxial with the tubes 2 2'. The bores 9 and I 0 are equal innumber andalternate so that there are two intercalated sets. the bores.IO'are closed at their opposite outer ends by the discs 1 and 9. In eachof the bores 9 is placeda controlling piston II, the space I2 (Figs. 1and 4) on one side of each piston II communicating through a port I3 inthe part 9 or the piston with one of the ports 3 of the tubes 2- 2",while the space I4 on the other side of each controlling piston Iicommunicates through a port IS with one of piston II has two groups ofdrilled ports I6, I1 circumferentially arranged as shown. I6 are portsprovided in the part 6 of the piston which are adapted to connect thespaces I2 with the space I of the cylinder 5, and il are correspondingports provided in the part 6 or the piston which are adapted to connectthe spaces I4 with the space I of the cylinder i. Engaging the severalcontrolling pistons II so as to partake of the axial motion thereof is acommon ring II the centre 01' which lies in the axis or the tubes 2 2Each oi the bores I9 is formed with a shoulder 23 or 25 asthe case maybe, the shoulders 23 being in the part land the shoulders 29 being inthe part 5. Combined bushings and spring seats 29 and M which formopposed sets are mounted in the bores I9 and are limited in their motiontoward each other by flanges 22 and 24'formed at their outer ends. Thesebushings are urged toward each other by coil compression springs 29 and27 which are mounted in the bores I9 and react against the cover plates1 and 9. In their innermost posi-' 'tion the bushings 29 and 2I centerthe ring I 9,

which is the dental clutch ring. To hold this ring against rotation andto guide its axial movement, tubular pins I9 are mounted in the ring I3and projectJn opposite directions therefrom, the projecting portions ofthe tubular pins being guided in the bushings 29 and 2l above 1described. The bushings are so dimensioned Each controlling accuratelycenter the clutch ring I9 but the latter may be forced in eitherdirection for a limited distance, in which event one set of springs 29or 21 is compressed and the other merely holds the correspondingbushings at their innermost positions.

Inside the axially movable cylinder I, is cut a multiple quick pitchscrew thread 29, the pitch with a series of teeth 33, which mesh with acorresponding series of teeth on the external periphery of the ring I9.

The way in which the apparatus described works is as follows:

In Figs '1 and 4 the various parts are' shown in their middle position.In this position the ring I9 prevents the ring .29 from rotating on themain piston formed by the parts 5, 9. The axially movable cylinder I istherefore locked.

If the propeller blades I02 are to be set or adjusted in a definiteposition, one group oi. ports 3 or 4 respectively is connected to thesource of medium under pressure, i. e. the pump H2, and the other group01' ports 4 or 3 respectively is connected with the discharge. Let itthat in their positions of closest approach they teeth II, alter thering 29 be assumed that medium under pressure flows in through pipe I09and the ports 3 and passes into the spaces I2 of the borings 9. If thepressure which arises in these spaces I2 exceeds the pressure exerted bythe springs 21, the controlling pistons II will be thrust downwards andthereby also the ring I8 'with which they are interengaged so that itsteeth will be brought out of engagement with the internal series of 39on the ring 29. This latter can now rotate freely. Owing to the abovementioned downward movement of the controlling pistons has been releasedfrom the ring I9, the ports I8 'are also opened so that now medium underpressure can pass out of the spaces I2 into the cylinder. space P. Onthe other hand a discharge of medium under pressure out o! the cylinderspace I through the Ports I1 and the borings H in the controlling pistonIi into the ports I! and out of these latter into the ports 4 isrendered possible. The

pressure which now prevails in the cylinder- As soon as the admission ofmedium under 7 pressure through the ports springs 21 are able to presstheir stops 24 against the stops 25 again, so that the ring I9 and thusalso the controlling pistons 3 is interrupted, the

II are brought back into their position. This causes the external seriesof teeth on the ring I9 to be brought intoengagement with the internalseries of teeth 33 on the ring 29, whereby the cylinder I is lockedagain. The teeth on the ring I9 are so constructed that they can bebrought into engagement with the teeth 33 on the ring 29 in everyperipheral position of the ring II. During the entire duration 01' thethe bushes 2i withpropeller shaft.

' under pressure middle position shown in the above operations thebushes 24 are pressedKby the springs 24 against the stops 24, so thatdur-J ing the above mentioned movement of the ring l4 out of its centralposition they have not exerted any force upon the latter.

The above described parts of the locking device proper are perfectlysymmetrically built; if therefore the ports 4 be connected to the pumpH2 and the ports 4 with the discharge, actions like those describedwilltake place, but with the difference that the cylinder 1 is then notdisplaced upwards, but downwards.

The constructional form shown in Figs. 6 and '1 differs from the onejust described by the .fact that the controlling pistons II, the ring l4and the pin-s l4 are grouped together into a single, axially movablering 44 the axis of which lies in the axis ofthe propeller. In this ring44 are provided, alternately from below and above. bores 4|, 42. Theaxes of these bores 41, 42 he on a cylindrical surface, the axis ofwhich 00-- incides with the axis of the tube 44, i. e. the In thesebores are arranged compression springs 44 and 44 respectively with theiraxes parallel with .the axis of the propeller. The springs 44bear-against the part 44 of the main piston and distance pieces 44,while the springs 44 bear against the part 41 of the main piston and thedistance pieces 44. When the ring 44 has been moved out of its centralposition in one direction or the other by the liquid under pressure, thesprings 43 and 44 tend to bring it back into its central position everytime. 44 denotes the axially movable cylinder, on the inside of which,as before, a screw thread is cut,

and '44 denotes a ring which is mounted to rotate on themain-pistonjormed by the parts 44, 41 and which has on its externalperiphery a screw thread 44, which engages in the screw thread on thecylinder 44, while an internal series ofteeth 42 on this ring 44 cancooperate with a series of teeth II on the ring 44. 44 and 44 denote twogroups of ports which are provided in the tube 44' and serve alternatelyfor the admission and discharge of a medium under pressure in the spaces41 and 41 respectively of the main piston. 44 (Fig. 'I) denotes guidecams which prevent the ring 44 from rotating relatively to th'e'mainpiston. v

' If medium under pressure be admitted through the group of ports 44 forexample, the pressure of the liquid in the annular space 41 acts on thering 44, which therefore is displaced upwards against the forces exertedby the springs 44. This causes its teeth 4| to be brought out ofengagement with the teeth 42 of they screw threaded ring 44.Simultaneously controlling ports 44 for the passage of medium underpressure from the annular space 41 to the space 44' of the cylinder 44are opened. On the other hand controlling ports 4|, which are incommunication with the space 42 of the cylinder 48, are connected byborings 44 in the ring 44 with the annular space 41 so that medium underpressure can flow out of the space 42 into the borings 42 and out ofthese latter through ports teeth 42 of the ring 44 and the lattertherefore locks the cylinder 44.

The way in which works is, owing to the symmetrical constructionthereof, the same in principle for both directions of motion of thecylinder 44. The advantage that no centrifugal versely on other .partsbut are absorbed in themselves.

What is claimed is:

1. The combination of a rotary shaft, 9. double acting fluid pressuremotor having opposed working spaces and comprising coacting cylinder andpiston elements mounted coaxially with said shaft and each constrainedto rotate therewith, one thereof being axially movable relatively to theshaft; a dental clutch ring concentric with the cylinder and pistonelements, swiveled as to one element and having quick pitch threadengagement with the othen; a coacting dental clutch disc axiallyshiftable but constrained against rotation relative to the element onwhich '44 into the ports 44. The ports 44, 4| are how-,

ever, only opened for the passage of medium brought out of engagement.If'no medium under pressure flows to the ports 44 and 44 respecafter theteeth 4|, 42 have been axial shifting'of the clutch portion;

said .clutch ring is swiveled and having a mid position in which itengages with the clutch ring to inhibit rotation thereof and oppositelydisplaced disengaged positions; yielding means biasing said clutch disctoward said engaging position; means for creating fluid pressuredifferentials in the working spaces of said motor; and fluid pressureoperated means responsive to the last named means to shift saidclutchring {selectively to said disengaging, positions while 7 suchdifferentials persist and permit return to engaging position as soon assaid pressure differential disappears.

2. The combination defined in claim 1 in which the clutch ring isswiveled on the periphery of the piston and engages quick pitch threadsin the cylinder wall and the axially shiftable clutch disc is mountedwithin the piston.

3. The combination defined in claim 1 in which the cylinder is theaxially shiftable element of the motor, and the piston is fixed on theshaft, the shaft and piston having ports formed therein leading to theworking spaces of the motor, the clutch ring is swiveled on theperiphery of the piston and engages threads formed in the cylinder wall,the clutch disc is housed in the-piston and the fluid pressure operatedmeans which shift the clutch disc metrically arranged valved pistonsconnected to shift the disc, controlling flow through said ports,shiftable by pressure differential developed therein and serving toobstruct said ports when the disc is in mid position and open them whenthe disc has been displaced to a disengaging position.

4. A blade adjusting propeller hub unit comprising in combination arotary shaft; a blade adjusting motor inclusive of a piston and acoacting cylinder forming two working spacesrespectively on oppositesides of the piston, both the cylinder and piston being coaxial with theshaft and constrained to rotate therewith and the cylinder being axiallyshiftable relatively to the shaft; blade adjusting means operable by thegagement with the cylinder, said ring .having within the piston aconcentric annular dental a mating annular dental .clutch disc. withinthe piston concentric with the shaft and constrained to rotate.therewith, said disc being axially shiftable in opposite directions todisengaged positions from a middle engaged posithis second lockingdevice I of the concentric type of construction is; forces of one partact-adcomprise a plurality of symcylinder; a ring swiveled on v thepiston and having quick pitch thread en- 5; The combination defined inclaim 4 in which the yielding means comprises circular series ofidentical symmetrically spaced coil springs, the

series being concentric with, and the axes of the coils parallel with,the axis of said rotaryshaft.

6. A blade'adjusting propeller hub unit comprising in combination arotary shaft; a blade adjusting motor inclusive of a piston and acoacting cylinder forming two working spaces respectively on oppositesides of the piston, both the cylinder and piston being coaxial with theshaft and constrained to rotate therewith and the cylinder being axiallyshiftable relatively to the shaft; blade adjusting means operable by theaxial shifting of the cylinder; a ring swiveled on the piston and havingquick pitch thread engagement with the cylinder, said. ring havingwithin the piston a concentric annular dental clutch portion; a matingannular dental clutch disc within the piston concentric-with the shaftand constrained to rotate therewith, said disc being axially shiftablein opposite directions to disengaged positions from a middle engagedposition; yielding means urging said disc to said engaged position;means for developing fluid pressure differentials between the workingspace of said motor, cluding ports in the shaft and piston for supplyingpressure fluid to either working sp ce while venting the other; and a.circumferential series of symmetrically spaced axes of the pistonsparallel with the axis of said shaft, said pistons obstructing flowthrough said ports except when said clutch disc is displacedsufficiently to disengage.

7. A blade adjusting propeller hub, unit comprising in combination arotary shaft; a blade adjusting motor inclusive of a piston and acoacting cylinder forming two working spaces respectively on oppositesides of the piston, both the cylinder and piston being coaxial with thetion; yielding means urging said disc to said shaft and constrained torotate therewith and the cylinder being axially shiftable relatively tothe shaft; blade adjusting means operable by the axial shifting of thecylinder; a'ring swiveled on the piston and having quick pitchthread'engagement with the cylinder, said ring having within the pistona concentric annular dental clutch portion; a mating annular dentalclutch disc within the piston concentricwith the shaft and constrainedto rotate therewith, said disc being axially shiftable in oppositedirections to disengaged positions from a middle engaged position;yielding means urging said disc to said engaged position, said meansincluding two opposed circular series of symmetrically spaced coilsprings, the series being concentric with and the axes of the coilsarallel with the axis of said rotary shaft; stops limiting the action ofsaid springs to define said engaged position;

means for developing fluid pressure diiferentials between the workingspace of said motor, including ports in the shaft and piston forsupplying f shift the same and shiftable by pressures developed in saidports,'the series being concentric with and the axes of the pistonsparallel with the axis of said shaft, said pistons obstructing flowthrough said ports except when said clutch disc is displacedsuiiicientlyto disengage.

- 8. The combination of a rotary shaft, a double acting fluid pressuremotor havingopposed working spaces and comprising coacting cylinder andpiston elements mounted coaxially with said shaft and each constrainedto rotate therewith, one thereof being axially movable relatively to theshaft; a ring concentric with the cylinder and piston elements swiveledasto one element and having quick pitch thread engagement with withinthe piston CURT KELLER.

